Receivers are small speakers used by many conventional portable electronic devices to produce sound. For example, the voice of a caller may be generated by a receiver of a conventional mobile phone. The receivers are attached to the device housing around the area in the device housing with the speaker hole. In this manner, receivers of conventional portable electronic devices project sound directly out of the speaker hole for listening by a user.
Given that the receivers are located behind the speaker hole of the device housing, the placement of the speaker holes for conventional portable electronic devices is constrained by the size and shape of the receiver. For example, the receiver is often pushed to the top of the device housing to make room for other components. As such, the speaker holes of many conventional portable electronic devices are located near the top of the device housing.
Conventional portable electronic devices with speaker holes located near the top of the device housing are generally uncomfortable to use given that the top edge of the device housing must be pressed into the user's ear. Additionally, the small distance between the speaker hole and the top of the device housing makes it more difficult for a user's ear to seal against the device housing around the speaker hole. As such, conventional portable electronic devices generally offer poor sound quality.
Back volume chambers are sometimes used in portable electronic devices to increase the sound quality of the receivers. The quality of the seal as well as the size and shape of the back volume chamber can affect the frequency bandwidth of the sound generated by the receiver. The back volume chambers of some conventional portable electronic devices are formed using sealant between walls of the device housing and other components (e.g., printed circuit boards). However, the seal created by the sealant often fails over time due to degradation of the sealant, relative movement between the printed circuit boards and the device housing, and the like. Additionally, the size and shape of the back volume chamber of conventional portable electronic devices is determined by the arrangement of the device housing and other components (e.g., printed circuit boards). Accordingly, the back volume chambers of conventional portable electronic devices offer limited improvement in sound quality.